Fish Larvae as Indicators of Cross-Ecosystem Subsidies in Great Lakes Coastal
Embayments

Project Summary

Great Lakes coastal tributaries and their associated vegetated, shallow, protected
embayments connect coastal watersheds to fisheries by serving as nursery grounds
for migratory fishes – their young rely on these habitats for feeding
and refuge – and by supporting a forage base for predatory fishes. The
water quality and fish habitat in these coastal ecosystems, however, are highly
vulnerable to degradation from human activities. Our goal is to help restore
healthy Lake Superior fisheries by identifying, conserving, and maintaining
the connections between coastal landscapes and coastal fishes.

We are interested in whether changes in the watershed alter how coastal habitats
support the production and growth of fishes. Our research uses chemical biomarkers
in fish larvae to describe the flow of energy and nutrients from the land to
the coastal aquatic food web. We are comparing six southwest shore river-embayment
systems – the St. Louis River and Duluth/Superior Harbor (MN), Pokegama
River and Pokegama Bay (WI), the Nemadji River and Allouez Bay (WI), the Amnicon
River (WI), and Fish Creek and Chequamegon Bay (WI). These river-embayment
ecosystems provide critical nursery habitat for priority Great Lakes fish such
as lake sturgeon and walleye. Due to their relatively fast response to environmental
conditions (i.e., days to weeks), their fish larvae could be used to test differences
with respect to landscape character, time, or hydrology. As indicators, fish
larvae could provide information on contributing sources (e.g., specific biomarkers
reflect anthropogenic or terrestrial origins) and demonstrate population-level
responses (e.g., nutritional status of early life stages, a potential indicator
for population success).